Why the same plate lands differently in two bodies.
Yes, partly. Your genes influence how fast your cells age at a biological level, but they are not the only thing driving the difference. Two people born the same year, eating the same diet, with similar medical histories can look and function very differently at 60.
How fast you turn carbohydrates into blood sugar is partly genetic, shaped by genes like AMY1 and TCF7L2 that vary a lot between people in the same family.